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Scheinost, J. C.

Publications and source records attributed to Scheinost, J. C..

2 recordsLinked to original sources
bioRxiv2019

Scc2 counteracts a Wapl-independent mechanism that releases cohesin from chromosomes during G1 but is unnecessary during S phase for establishing cohesion

Cohesins association with chromosomes is determined by loading dependent on the Scc2/4 complex and release due to Wapl. We show here that Scc2/4 is not merely a loading complex and that it actively maintains cohesin on chromosomes during G1. It does so by blocking a Wapl-independent release reaction that requires opening the cohesin ring at its Smc3/Scc1 interface as well as the D loop of Smc1s ATPase. The Wapl-independent release mechanism is switched off as cells activate Cdk1 and enter G2/M and cannot be turned back on without cohesins dissociation from chromosomes. The latter phenomenon enabled us to show that cohesin that has already captured DNA in a Scc2-dependent manner before replication no longer requires Scc2 to capture sister DNAs during S phase.

molecular biology↗
bioRxiv2018

The topology of DNA entrapment by cohesin rings.

Cohesin entraps sister DNAs within tripartite rings created by pairwise interactions between Smc1,Smc3, and Scc1. Because the ATPase heads of Smc1 and Smc3 can interact with each other, cohesin rings in fact have the potential to form a variety of sub-compartments. Using in vivo cysteine crosslinking,we show that when Smc1 and Smc3 ATPases are engaged in the presence of ATP (E heads)cohesin rings generate a \"SMC (S) compartment\" between hinge and E heads and a \"kleisin (K)compartment\" between E heads and their associated kleisin subunit. Upon ATP hydrolysis, cohesins heads associate with each other in a very different mode, in which their signature motifs and their coiled coils are closely juxtaposed (J heads), creating alternative S and K compartments. We show that all four sub-compartments exist in vivo, that acetylation of Smc3 during S phase is accompanied by an increase in the ratio of J to E heads, and that sister DNAs are entrapped in J-K but not E-K compartments or in either type of S compartment.

molecular biology↗